This invention relates to a method of forming as-cast holes by using cores in a die-casting mold which is opened and closed using a hydraulic cylinder. This invention also relates to an apparatus for practicing the method.
It has previously been proposed that where a casting is to be formed with a die-casting mold having undercuts or as-cast holes which cannot be formed using only stationary and movable dies, a core which is movable in the direction of formation of the undercuts or as-cast holes be provided in the mold.
For instance in the case of forming a casting a which has undercuts b and j and as-cast holes c and d as shown in FIG. 1(a), the undercuts b and j and the as-cast hole c can be formed by sliding a core die e in the directions of the arrow g--g' by use of a hydraulic cylinder. However, it is impossible to form the hole d by using the core die e because the hole d is perpendicular to the directions of the arrow g--g'.
In order to form the hole d, it would be necessary to provide a protrusion e' in the core die e; as shown in FIG. 1(b), but since the core die e is moved in the directions of the arrow g--g', such a protrusion is not possible from a practical standpoint.
FIG. 2 shows an example of another proposed method for forming an as-cast hole i. This method involves use of a dual core e and h in which hydraulic cylinder f forms an angle with the directions g--g' for sliding the core die e. However, even in this method, the angle of formation of the hole i with respect to the directions g--g' of the core die e is limited. That is, it is impossible to form an as-cast hole the axis of which forms right angles (or an acute angle close to right angles) with the slide direction g--g'.
Therefore, the as-cast hole d has been formed as follows: The part of the casting where the hole d is to be formed is molded relatively large in wall thickness, and is then machined to form the hole in another manufacturing step. Formation of the hole d is thus troublesome. Moreover, there is a likelihood that cavities will be formed in the casting due to the large wall thickness.